I. Field of the Invention
This invention relates generally to heat recoverable articles used to form a seal between a substrate and a bounded opening through which the substrate extends and methods incorporating the use of such articles. More specifically, it relates to a laminated sealing article comprising at least one wafer of radially expanded, cross-linked, dimensionally heat unstable polymeric material and a layer of adhesive bonded thereto.
II. Description of the Prior Art
Forming an environmental seal between a single substrate and an opening through which the substrate passes is a frequently encountered problem to which many solutions are known. For example, if the gap between the opening and the substrate is small, the gap can be filled with a suitable caulking compound. Alternatively if the opening is provided with an outwardly extending flange, a section of heat shrinkable tubing can be recovered around both the flange and the substrate thereby forming the desired seal. The sealing problem becomes more difficult when the gap between the substrate and the opening is large and/or when two or more substrates extend through the same opening. Much difficulty is encountered with a plurality of substrates because all of the gaps between the substrates must be sealed.
One specific multiple substrate sealing problem occurs in aircraft wiring harnesses where a plurality of individually insulated electrical conductors enter the rear of a multiple contact connector. Because the individual conductors must be removable and replaceable, an epoxy resin or other functionally similar permanent potting compound cannot be used to seal the rear of the connector. Currently, many connector manufacturers employ a resilient multi-apertured sealing grommet of silicon rubber or the like to form a seal around each conductor as it enters the rear of the connector. The apertures in the sealing grommet which correspond to unused contacts in the connector are sealed with removeable plastic pins. In both principle and practice this sealing arrangement is quite satisfactory as long as all of the conductors extend straight back from the rear of the connector. However, because of dense equipment packaging requirements, it is not unusual to find installations where the individual conductors are disposed at right angles to the rear of the connector. In such installations where a conductor is pulled sideways, the corresponding aperture in the sealing grommet is distorted from a circular configuration to an oval one and the seal between the grommet and the conductor is broken. Water which can condense on the conductors frequently flows along the conductor's surface and into the connector causing electrical malfunctions which can ground the aircraft.
Analogous sealing problems occur in buildings where wires, cables, tubing, pipes, electrical conduits, heating and cooling ducts and the like pass through walls or partitions. Environmental seals are frequently required in such locations to provide protection against, for example, fire, moisture, dust, heat, cold, noise, pressure differentials, bacteria, insects, rodents and other pests, toxic chemicals, radioactive materials and the like. Although many techniques are known for sealing the gaps between such substrates and openings, all suffer from at least one disadvantage.